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A spokesman for Karbala told the BBC that as hundreds of thousands of pilgrims ran through the streets, one person stumbled and fell other, causing others to fall and triggering the deadly stampede.

Security officials have said a walkway collapsed during the crush.

Authorities have warned the death toll is likely to rise.

Karbala, around 62 miles south of the Iraqi capital Baghdad, was the site of a major battle in the year 680, which led to Husayn's death.

KARBALA, IRAQ - SEPTEMBER 10: People, affected from the stampede, receives medical attention from Iraqi health team, on September 10, 2019 in Karbala, Iraq. At least 31 people were killed and 100 others were wounded in a stampede during the Ashura ceremony in the southern province of Karbala. (Photo by Stringer/Anadolu Agency via Getty Images) (Image: Getty)

Authorities have warned they expect the death toll to rise (Image: Getty)

The day is marked as a national holiday in several countries, including Afghanistan, Bahrain, Iran, Iraq, Lebanon and Pakistan.

One of the rituals is called the "Tuwairij run" which sees pilgrims run down the streets towards the Imam Hussein Mosque.

It commemorates the run from the ancient village of Tuwairij to Karbala, undertaken during the seventh century battle by the cousins of Husayn's half-brother Abbas.